Air conditioning, by its name means treating air with a view to altering its temperature and moisture content with the use of refrigeration, it is necessary that we should know how exactly air would behave when it is subjected to cooling, heating, humidifying or dehumidifying processes.

For this purpose, it is necessary to study the property of air at normal atmospheric pressure in so far as it concerns air conditioning. Such a  study is what is called psychometrics.

For the study of psychometric, a chart has been devised, which is called Psychrometric Chart. We will see what are the various lines of the psychrometric chart are